The present invention relates generally to photographic apparatus and film assemblages for use therewith and, more specifically, to improvements regarding methods and apparatus for processing such film units in a photographic apparatus.
Heretofore, the prior art relating to so called instant film technology encompasses film assemblages that are removed manually from cameras of the self-developing type. These film assemblages include two sheets of flexible photographic material and a rupturable reservoir containing processing fluid. The rupturable reservoir includes a weakened portion that ruptures upon the application thereto of predetermined compressive forces that are applied by a pressure applying assembly during film assemblage removal. It is extremely important for the successful development of latent images on the photographic material that the fluid be spread in a layer relatively uniformly throughout the extent of the photosensitive layer. Therefore, a series of parameters have been established whereby the width of the pressure applying area, the viscosity of the processing fluid and the rate at which the sheet materials are withdrawn through a pressure applying nip, the shape of the pressure applying members and the pressure generated ensure that the spreading of the processing fluid occurs at a substantially uniform pre-determined thickness regardless of variations in thickness of the materials, the viscosity of the liquid and the speed of movement of the sheet materials through the pressure applying members. In addition, the pulling of the film along a plane generally perpendicular to the film exit is also desired to maintain the uniform layer. However, there is no control of the direction of tension applied to the sheets and the angular direction by which the film exits the cameras. As a result, it may be that a film assemblage is withdrawn at an angle with respect to a desired pulling plane that includes the bite line of the pressure-applying members. Such angular deviation results in a lack of thickness uniformity of the processing fluid layer that is spread between the sheets and thereby results in image artifacts.
Known attempts to overcome this problem are described in, for example, commonly assigned U.S. Pat. No. 2,845,850 camera having a device that defines a passage or gap that is spaced from the camera's film exit slot. The size of such passage is such that while pressure is not applied on the sheets as they move through the passage, the angular deviation of the sheets from the desired pulling plane is limited. However, sharp bending of the sheets around leading edges or lips of this device is problematic and could result in separation of the two sheets with attendant image artifacts being created in the developed image.
While it is been known to address the problem of non-uniform spreading of processing fluid between superposed sheets of photosensitive material of the self-developing type, it is nevertheless, desired to improve upon heretofore known approaches.